text: /* ----------------------------------------------------------------------
   * Project:      CMSIS DSP Library
   * Title:        arm_scale_q7.c
   * Description:  Multiplies a Q7 vector by a scalar
   *
   * $Date:        27. January 2017
   * $Revision:    V.1.5.1
   *
   * Target Processor: Cortex-M cores
   * -------------------------------------------------------------------- */
  /*
   * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
   *
   * SPDX-License-Identifier: Apache-2.0
   *
   * Licensed under the Apache License, Version 2.0 (the License); you may
   * not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an AS IS BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include "arm_math.h"
  
  /**
   * @ingroup groupMath
   */
  
  /**
   * @addtogroup scale
   * @{
   */
  
  /**
   * @brief Multiplies a Q7 vector by a scalar.
   * @param[in]       *pSrc points to the input vector
   * @param[in]       scaleFract fractional portion of the scale value
   * @param[in]       shift number of bits to shift the result by
   * @param[out]      *pDst points to the output vector
   * @param[in]       blockSize number of samples in the vector
   * @return none.
   *
   * <b>Scaling and Overflow Behavior:</b>
   * \par
   * The input data <code>*pSrc</code> and <code>scaleFract</code> are in 1.7 format.
   * These are multiplied to yield a 2.14 intermediate result and this is shifted with saturation to 1.7 format.
   */
  
  void arm_scale_q7(
    q7_t * pSrc,
    q7_t scaleFract,
    int8_t shift,
    q7_t * pDst,
    uint32_t blockSize)
  {
    int8_t kShift = 7 - shift;                     /* shift to apply after scaling */
    uint32_t blkCnt;                               /* loop counter */
  
  #if defined (ARM_MATH_DSP)
  
  /* Run the below code for Cortex-M4 and Cortex-M3 */
    q7_t in1, in2, in3, in4, out1, out2, out3, out4;      /* Temporary variables to store input & output */
  
  
    /*loop Unrolling */
    blkCnt = blockSize >> 2u;
  
  
    /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
     ** a second loop below computes the remaining 1 to 3 samples. */
    while (blkCnt > 0u)
    {
      /* Reading 4 inputs from memory */
      in1 = *pSrc++;
      in2 = *pSrc++;
      in3 = *pSrc++;
      in4 = *pSrc++;
  
      /* C = A * scale */
      /* Scale the inputs and then store the results in the temporary variables. */
      out1 = (q7_t) (__SSAT(((in1) * scaleFract) >> kShift, 8));
      out2 = (q7_t) (__SSAT(((in2) * scaleFract) >> kShift, 8));
      out3 = (q7_t) (__SSAT(((in3) * scaleFract) >> kShift, 8));
      out4 = (q7_t) (__SSAT(((in4) * scaleFract) >> kShift, 8));
  
      /* Packing the individual outputs into 32bit and storing in
       * destination buffer in single write */
      *__SIMD32(pDst)++ = __PACKq7(out1, out2, out3, out4);
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
     ** No loop unrolling is used. */
    blkCnt = blockSize % 0x4u;
  
    while (blkCnt > 0u)
    {
      /* C = A * scale */
      /* Scale the input and then store the result in the destination buffer. */
      *pDst++ = (q7_t) (__SSAT(((*pSrc++) * scaleFract) >> kShift, 8));
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
  #else
  
    /* Run the below code for Cortex-M0 */
  
    /* Initialize blkCnt with number of samples */
    blkCnt = blockSize;
  
    while (blkCnt > 0u)
    {
      /* C = A * scale */
      /* Scale the input and then store the result in the destination buffer. */
      *pDst++ = (q7_t) (__SSAT((((q15_t) * pSrc++ * scaleFract) >> kShift), 8));
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
  #endif /* #if defined (ARM_MATH_DSP) */
  
  }
  
  /**
   * @} end of scale group
   */
  